The mammalian NADH dehydrogenase (complex I), which is under dual genetic control, nuclear and mitochondrial, plays a central role in oxidative phosphorylation. This respiratory complex consists of 45 subunits and has been implicated in human genetic and acquired diseases. In previous studies, we have isolated several cell lines deficient in complex I assembly and mitochondrial function. We further identified a putative protein factor whose over-expression was associated with recovered complex I assembly. The specific aims of the proposal are to 1) determine if the protein we identified is a complex I assembly factor 2) to develop a genetic approach to isolated genes that could compensate mitochondrial deficiency caused by complex I gene mutations. The success of this proposal will help us to understand the regulation of assembly and function of respiratory complex I, and also provide useful clues for developing a therapeutic approach for complex I deficiency. PUBLIC HEALTH RELEVANCE: We submit this grant application focusing on understanding the function and regulation of mitochondrial respiratory complex I. In particular, we will develop a novel approach to isolate important protein factors which regulate mitochondrial function. The success of this project will advance our understanding of mitochondrial function and shed light on the pathogenesis of human disease associated with complex I dysfunction.